The Three Dimensional Changes of the Lower Teeth with the Rocking Chair Archwire of Niti Round or Square
|Rocking chair NiTi round archwire NiTi square archwire Three dimensional change Open bite bite opening
Objective:To observe the three-dimensional change tendency of lower arch when NiTi round or squared rocking chair archwire was used to open overbite in patients of Angle Class I or Class II with I or II degree deep overbite. The objective includes the changes of the curve length and width of dental arch, the changes of the labial-lingual and intruding-extruding of the lower anterior teeth in labial-lingual and intruding-extruding directions, the changes of the buccal-lingual and intruding-extruding of the anchorage teeth in the buccal-lingual and intruding-extruding directions. Analyze the results obtained from different usage of rocking chair archwire and provide a theoretical clinical refenrence. using the different NiTi archwires and fixed methods.Methods:Choose 40 patients,17 boys and 23 girls, between 13 to 17 years old(16.4 on average), who were Angle Class I or Class II with I orⅡdegree deep overbite were chosen. All the patients were divided into two groups according to the different archwire. And each group was divided into two groups:one group using laceback and cinch back and the other not. The patients were taken standardized lateral cephlograms and gypsum gnathodes before and after the overbite opened by using the typical swinging chair labial arch. Some hard and soft tissue landmarks were selected and evaluated. Use the laser scan and Imageware software were used to do the digital model analysis. All data were analyzed by SPSS 12.0 software to study the correlation of the changes among the groups. Results:There were some significant changes of lower teeth and dental arch when rocking-chair archwire was used to level the lower curvilinear.1. Changes of the arch width:There was no significance significant change in arch width between the canines and premolars(P>0.05). The width between molars was increased. There was no significance significant change between in the two groups with or without laceback and cinch back or not(P>0.05).2. Changes of arch curve length:The arch length of every each group was increased. The changes of the groups using laceback and cinch back were less significant comparing compared with the others(P<0.05).3. Changes of teeth in intruding-extruding direction:The incisors were intruded and but the canines changed little. The second premolars were elevated. And the mesio-buccocusp of the first molar didn’t move while the apo-buccocusp was depressed.4. Changes of teeth in mesial-distal direction:When using NiTi round archwire, the group with laceback and cinch back, incisiors made little labial movement, canines made distal movement, while the second premolars and the first molars changed little. When using NiTi round archwire, the group without laceback and cinch back, incisiors made labial movement, canines made little distal movement, premolars made little changes in mesial-distal, while molars had the tendency to move distally. distal. When using NiTi square archwire, the group with laceback and cinch back, incisiors made labial movement, canines made distal movement, the second premolars changed little, the first molars had little distal movement but the dental crown had the tendency to move buccallybuccal. When using NiTi square archwire, the group without laceback and cinch back, the tendency of incisiors labial movement was more significant, canines had the tendency of distal movement but not obvious, the second premolars had little changes, the first molars had the tendency of distal movement and lingual movement.5. Comparing Compared the lateral cephlograms of before and after treatment pretreatment and posttreatment, there was no significant difference change of on the location of B point and its measurement angles(P>0.05). While the location and angles of LI point and its measurement angle changed obviously(P<0.05), and there was significant difference between the four groups using different archwires and different fixed methods(P<0.05).Conclusion:Rocking chair archwire is used for bite opening to open overbite of the patients of Angle Class I or Class II, it will makes teeth change in three dimensions. The morphous of the arch does not changes obviously.unobviously. The width between molars increases while the width between the canines and premolars changes little. The location and angle of the lower teeth change obviously. The location of the lower teeth changes. The incisors are intruded and have the tendency of labioclination, the incisor its labioclination tendency is more significant with in laceback and cinch back group. The canines show the tendency of apoclination and there are obvious changes with the laceback and cinch back, while the intruding-extruding changes is are not obvious. The second premolars are elevated. And the The mesio-buccocusp of the first molar does not move while the apo-buccocusp is intruded. The first molars have the tendency of distal movement and lingual movement when using NiTi square wire. In the process of overvite open bite opening,using rocking chair labial arch, there are different mandibular arch three-dimensional changes with round or square archwire, with or without laceback and cinchback. it is different in using round or square archwire, with or without laceback and cinchback on the three-dimensional change of the lower incisors.